* { margin: 0; padding: 0; }
body { background-color: #efeff4; }
html, body { height: 100%; }
#box { height: 100%;}
.main { display: flex; flex-direction: column; height: 100%;}
header { height: 44px; line-height: 44px; text-align: center; border-bottom: 1px solid red;}
footer { height: 50px; line-height: 50px; border-top: 1px solid red; display: flex;}
footer a { flex: 1; text-align: center;}
section { flex: 1; overflow-y: auto;}